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In the latest StarTalk NDT says that without friction space crafts would not be able to slow down when reentering orbit. The friction against the air slows it down from 17,000 miles per hour down.

There have been animals that have been found to create something close to zero disturbance as they move through the water. Is this friction reduction? I can't find the article now but I think it was sharks or alligators. And some beetles have shell structure that water rolls off of.

Are there any frictionless objects or is it possible to create frictionless objects?

https://www.youtube.com/watch?v=XJcFWR9LrBU

Super conductors

https://youtu.be/wlvHD6N5Gkk

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  • $\begingroup$ Friction can be reduced but eliminated. Think about the fish example, if they are truly frictionless in the water, they don't need to move their body parts continuously to advance their position (one propel should do), and how are they going to stop their motion? $\endgroup$ – r13 Apr 9 at 19:39
  • $\begingroup$ Aren't superfluids frictionless? I think that's the only thing that is although there's probably some super gnarly stuff inside neutron stars and the like. However, "water rolls off" could simply mean laminar flow or even that the surface doesn't get wetted by the fluid due to low surface energy (i.e. surface tension). $\endgroup$ – DKNguyen Apr 10 at 0:56
  • $\begingroup$ @DKNguyen Aren’t super conductors frictionless? youtu.be/wlvHD6N5Gkk $\endgroup$ – 1.21 gigawatts Apr 10 at 1:38
  • $\begingroup$ @1.21gigawatts I suppose you could think about them as frictionless too if you want. It gets really murky with super conductors though since they can still have inudctance and can radiate energy via EM waves and such. You can also stuff so much current through a super conductor that it is no longer a super conductor. $\endgroup$ – DKNguyen Apr 10 at 2:11
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The content below is excerpted from the liked article FYI.

"Engineers have obsessed over submarine design for more than 200 years, but they've been unable to eliminate one of its most vexing problems -- friction drag, a force that opposes forward motion as water sticks to the surface of the outer hull. According to some estimates, this "skin friction" accounts for roughly 65 percent of the drag on submarines [source: Pike].

One solution? A polymer ejection system. In such a system, polymer is stored in a tank and then ejected through a series of ports as the submarine moves. The polymer flows over the surface and reduces the interaction of water molecules with the surface. Unfortunately, the system also increases the weight of the vessel.

Now scientists may have a better trick: coat submarines with a nonstick surface made from a revolutionary nanotechnology. The material doesn't look extraordinarily special to the naked eye. But if you view it under a microscope, you see that it contains tiny needles spaced just a couple millionths of a meter apart. The needles rest, like a layer of grass, on a surface of Teflon. When water hits the material, it encounters air trapped in the spaces between the needles. And this makes the material extremely slippery -- 99 percent less sticky than a normal Teflon surface without the nano-sized needles [source: BBC News]."

10 Crazy Uses for Completely Frictionless Surfaces

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